i wanted to make a flask that you can cast. my design came out a little bigger than an ender 3 bed so i included a split set to fit. 1/4 inch rods to align the faces.

the partial holes are roughly sized for drilling and tapping an m5 thread directly into the piece, but plenty of space around to size up to your needs.

at the center the flask is 5.5" x 8"

i have not tested this yet, will update when i do